Fat Soluble Vitamins: D, E & K

A fat-soluble vitamin that is important for calcium absorption and bone health. It is naturally found in foods like fatty fish, egg yolks, and cod liver oil.

A form of vitamin D produced in the skin from 7-dehydrocholesterol upon exposure to UV rays (sunlight).

A form of vitamin D produced from ergosterol (a plant sterol) by UV irradiation. It can also be found in some foods, especially fortified options.

A sterol precursor to vitamin D3 found in human skin. It is converted to vitamin D3 when exposed to ultraviolet radiation.

A sterol precursor to vitamin D2 found in plants and fungi. It is converted to vitamin D2 upon exposure to UV irradiation.

The process by which vitamin D is synthesized in the skin when exposed to ultraviolet B (UVB) radiation from sunlight.

Dietary sources of vitamin D, such as fatty fish, egg yolks, and fortified foods. These sources provide preformed vitamin D that can be directly absorbed by the body.

Supplements containing vitamin D, which can be taken orally to meet the recommended daily intake.

The major storage form of vitamin D, produced in the liver by the enzyme 25-hydroxylase.

The active form of vitamin D, produced in the kidneys by the enzyme 1-alpha-hydroxylase.

The mechanism by which calcitriol regulates calcium and phosphorus absorption in the intestine.

The mechanism by which calcitriol regulates calcium and phosphorus reabsorption in the kidney.

The role of calcitriol in bone formation and resorption.

A steroid hormone that regulates calcium and phosphorus metabolism.

A synthetic compound that acts as Vitamin K. It is used as a dietary supplement.

An enzyme that requires Vitamin K as a cofactor. It converts glutamic acid residues in blood clotting factors to γ-carboxyglutamic acid.

A modified glutamic acid residue found in blood clotting factors. It binds calcium, essential for blood clotting.

A protein found in bone that plays a role in bone mineralization by tightly binding to hydroxyapatite crystals. Its function depends on γ-carboxylation.

These drugs are structural analogs of Vitamin K and competitively inhibit γ-glutamyl carboxylase, leading to reduced blood clotting.

Vitamin D enters the cell and binds to a nuclear receptor called Vitamin D receptor (VDR). VDR then combines with Retinoic Acid X Receptor (RXR) forming a heterodimer that interacts with specific DNA sequences called Vitamin D Response Elements (VDREs) in the promoter region of target genes. This interaction regulates the expression of these genes, ultimately mediating vitamin D's biological activity.

Calbindin is a protein that facilitates the transport of calcium across intestinal epithelial cells, increasing calcium absorption in the gut.

Vitamin E, a potent antioxidant, acts primarily in the lipid phase of cells, protecting them from damage caused by free radicals.

Vitamin E protects red blood cells (RBCs) from hemolysis by preventing the peroxidation of lipids within the cell membrane.

Vitamin E protects vitamin A and carotenoids from oxidative destruction by free radicals, ensuring their stability and function.

Vitamin E can reduce the risk of atherosclerosis by preventing the oxidation of LDL cholesterol, a key factor in plaque formation within blood vessels.

Vitamin E is an important cofactor in the electron transfer system within mitochondria, playing a role in cellular energy production.

Selenium, another antioxidant, acts as a second line of defense, complementing the effects of Vitamin E by reducing its dietary requirement. Selenium is also essential for normal pancreatic function, which enhances the absorption of Vitamin E.